1. Field of the Invention
The present invention relates to a ruler, and particularly relates to improvement of a ruler having an arch member to be pressed on an upper surface of a ruler body for allowing side edges of the ruler body to closely contact on a surface of a target object.
2. Description of Related Art
Applicants and inventors of the present case heretofore have filed patent applications concerning a ruler with good work efficiency to be a guide for drawing a line or performing cutting by using a cutter by closely abutting on a target object, and three applications have matured into patents. A factor playing a central role in respective rules is that an arch member for giving a force of allowing the ruler to closely contact the surface of the target object is provided on an upper portion of the ruler body, and the contents of the technique are disclosed in Japanese Patent No. 4278207 (Patent Document 1), Japanese Patent No. 4384764 (Patent Document 2) and Japanese Patent No. 5137328 (Patent Document 3).
However, the high accuracy is pursued in the structure of the ruler in related-art examples, in which the arch member is supported by ribs (standing walls) of the ruler body by using pivot shafts, therefore, operations of adjusting a pitch and specifying a position are complicated, and further, the yield is low and the structure may not be suitable for mass production, which is a factor that increases costs.
When the ruler body and the arch member are formed by using different materials respectively, it is difficult to assemble them due to the difference in expansion coefficients, contraction coefficients and the like, and further, the selection of materials becomes uniform.